1. Field of the Invention
This invention relates to a ring interconnection network system formed by connecting a plurality of ring networks with a self-healing function to each other, node equipment and network management equipment and a path setting method used in the system. This type of network architecture is known as Ring Interconnection or Ring Interworking, which has been described in, for example, ITU-T (Telecommunication Standardization Sector of ITU) Recommendation G. 842 distributed by the ITU (International Telecommunication Union).
2. Description of the Related Art
A traffic self-healing method that is completed in a ring network has been described in ITU-T Recommendation G. 841. In this recommendation, this type of self-healing method is referred to as APS (Automatic Protection Switching).
In Annex A to the recommendation, measures to avoid failures known as Transoceanic Applications have been described. By the Transoceanic Applications, the communication path can be detoured to the shortest route that avoids the fault segment. This makes it possible to shorten the transmission distance of the path, which enables switching with less impact to be realized in a system with a long distance between nodes (or a large delay in transmission).
On the other hand, in ITU-T Recommendation G. 842, a method of interconnecting a plurality of ring networks has been described. In this recommendation, a method of restoring the traffic in a ring interconnection network system has been explained.
Recommendation G. 842, however, has explained only a failure avoiding method using a so-called non-Transoceanic method that avoids a failure. Therefore, Recommendation G. 842 has not disclosed a failure avoiding method using the above-described Transoceanic method.
This prevents operators who offer node equipment from becoming multi-vendors, which means that it is difficult to meet the needs of today's carrier operators. Furthermore, when the APS function according to Recommendation G. 841 Annex A and the interworking function according to Recommendation G. 842 operate independently, the communication can be disconnected or the traffic can be misconnected. Therefore, any measure to deal with this problem must be taken as soon as possible.
Furthermore, when the interworking function according to Recommendation G. 842 is realized, the following problem is encountered. In a network system, there is provided network management equipment to provide monitoring control of the system. In a conventional system taking no account of interconnection, the network management equipment can be regarded as each of the ring networks being an independent one. In this case, the network management equipment has only to manage the paths existing only in each ring network.
However, a system with an interconnection function has such paths as are set over a plurality of ring networks. Therefore, the network management equipment must manage such paths as well.
In such a situation, to grasp the path configuration, the operator has no choice but to combine manually the results of path management performed on a ring network basis in the conventional system. This takes a lot of time and labor for the operator to do it.
Furthermore, the path restoration process in such a ring interconnection network system is complex. This makes it more difficult for the operator to grasp the state of each path. For this reason, there is a need to improve the human-machine interface of the network management equipment and increase the convenience of the system operation.
As described above, a failure avoiding method using the Transoceanic method has not been provided in the ring interconnection network system. As a result, if switching by the Transoceanic method is effected in this type of system, there is a possibility that the line will be disconnected or the traffic will be misconnected.
Furthermore, since managing the paths requires a lot of time and labor in the conventional network management equipment, there is a need to decrease the required time and labor and improve the convenience of the system operation.